(a) Field of the Invention
The present invention relates an EGR coolant control system. More particularly, the present invention relates to an EGR coolant control system that may control a flow of coolant which is supplied to an EGR cooling apparatus, an oil cooler, and so on, so that cooling efficiency may be enhanced.
(b) Description of the Related Art
An exhaust gas recirculation (“EGR”) system is provided to a vehicle for reducing noxious exhaust gas.
Generally, NOx is increased in a case where an air ratio of an air-fuel mixture is high, which is necessary for sufficient combustion. Thus, the exhaust gas recirculation system mixes exhaust gas from an engine with the air-fuel mixture, for example at 5-40%, thereby reducing the amount of oxygen in the air-fuel mixture and retarding combustion, and so lessening generation of NOx.
Generally, the temperature of exhaust gas from an engine is very high, and so a cooling apparatus for cooling recirculation exhaust gas is provided therewith.
An oil cooler, a radiator, and so on need cooling in an operation of a vehicle, and, generally, the flow rate of the required coolant for cooling is increased in proportion to rotation speed of an engine.
The coolant flow rate for cooling the EGR cooling apparatus, the oil cooler, and so on is supplied in proportion to rotation speed of an engine.
As shown in FIG. 1, as the coolant rate is increased, the slope of EGR cooler efficiency is gradually decreased.
That is, when the coolant is simultaneously supplied to the EGR cooling apparatus and the oil cooler in proportion to rotation speed of an engine, the coolant is excessively supplied to the EGR cooling apparatus at a high speed and the coolant is insufficiently supplied to the oil cooler at a high speed. Thus, cooling efficiency is deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.